Cellular Automaton Simulation of Dendrite Growth in Solidification Process of Cr17 Stainless Steel under Mechanical Vibration

Abstract

Herein, a coupled model of temperature field and dendrite growth is built to examine the solidification microstructure of Cr17 stainless steel under vibration. The temperature field is calculated with ANSYS FLUENT software. In addition, considering solute diffusion and local curvature, a low grid anisotropic cellular automaton (CA) model is used to simulate the dendrite growth. To verify the major source of crystal nucleus in the melts, a mechanical model of dendrite fracture is built, and an investigation is conducted on the critical condition of grain dissociation. As indicated from the results, the dendrites are stripped and dissociated into the melt when the vibration frequency and amplitude values exceed the critical condition of dendrite fracture, the grains are dissociated more easily, and the more equiaxed grains are indicated in the melt with the increase in the vibration frequency. It is preliminarily demonstrated that vibration can facilitate the dendrites to break and be dissociated from the chilling generator surface. The simulation results comply with the experiment.

Review on Cellular Automata for Microstructure Simulation of Metallic Materials

“…However, due to the high crystallization temperature of ferritic stainless steel and the surface of the nucleus generator rapidly forming a solidification shell because of the effect of excited cooling, the difficulty of real-time observation of the solidification process undoubtedly increases. Wang et al [ 42 ] established a 2-D CA model of dendrite growth to simulate the solidification microstructure of Cr17 stainless steel processed by the vibration-excited liquid metal nucleation. The simulation results show that with the increase in vibration intensity, the temperature field distribution became more uniform, the area of the equiaxial dendrite zone was significantly enlarged, the grains were refined and the microstructure became more uniform, as shown in Figure 7 [ 42 ].…”

“…Wang et al [ 42 ] established a 2-D CA model of dendrite growth to simulate the solidification microstructure of Cr17 stainless steel processed by the vibration-excited liquid metal nucleation. The simulation results show that with the increase in vibration intensity, the temperature field distribution became more uniform, the area of the equiaxial dendrite zone was significantly enlarged, the grains were refined and the microstructure became more uniform, as shown in Figure 7 [ 42 ]. Furthermore, the formation of the solidified shell on the crystal nucleus generator surface was delayed.…”

“… The solute concentration distributions of dendrite growth under different vibrations. ( a – f ) 400, 500, 600 Hz, 0.2 mm, ΔX¼ 1 μm, 1000 × 1000 meshes, respectively [ 42 ]. …”